Moving web energized static eliminator and method

ABSTRACT

Apparatus for discharging or eliminating static electricity from a moving web, which is energized by the moving web. An insulating body carries a floating conductive plate, preferably annular, having an exposed surface, and a grounded conductive point having its tip capacitively spaced from the surface of the floating conductive plate. A method for reducing or eliminating static electricity from a moving web comprising establishing a floating conductive plate in capacitive relationship with the moving web, and establishing a grounded conductive point in capacitive relationship with the floating conductive plate.

United States Patent [1 1 [111 3, Testone [45] Nov. 18, 1975 MOVING WEB ENERGIZED STATIC Primary Examiner-J. D. Miller ELIMINATOR AND METHOD Assistant Examiner-Harry E. Moose, Jr. [76] Inventor: Anthony Q. Testone, P. O. Box 414, Attorney Agent or Flrm lrvm Lavme Lee, Mass. 01238 [22] Filed: May 16, 1974 [57] ABSTRACT Apparatus for discharging or eliminating static elec- PP -z 470,700 tricity from a moving web, which is energized by the moving web. An insulating body carries a floating con- 52 US. Cl. 317/2 F; 317/4 ductive plate, P e y annular, having an exposed 51 int. c|. H05F 3/00 Surface, and a grounded Conductive Point having its [53] n w f Search 317 R, 2 A, 2 D, 2 E, tip capacitively spaced from the surface of the floating 317 2 1: 3 4 2 324/32, 109, 149 conductive plate. A method for reducing or eliminating static electricity from a moving web comprising [5 References Cited establishing a floating conductive plate in capacitive UNITED STATES PATENTS relationship with the moving web, and establishing a 1 208 238 121916 T k t l /2 R grounded conductive point in capacitive relationship 00 Cl e a 3,163,753 12/1964 Di Sabato et al. 317/262 R wlth the floatmg conductive plate' 13 Claims, 4 Drawing Figures e g s U.S. Patent Nov. 18,1975 3,921,037

AND METHOD BACKGROUND OF THE INVENTION The present invention relates to an apparatus and method for eliminating or reducing static electricity present in a moving web of material.

It has long been known that static electricity occurs in moving webs of material, used in machines in different arts. These include, by way of example, paper handling machines and textile processing machines. The static electricity interferes with the operation of the machines and the handling of the products being processed in or on the machines, and for that reason many machines are equipped with devices known as static eliminators or static bars. The term static eliminator is generally used, although it is not necessary that the device eliminate the entire static charge on a moving web. The term static bar is used because the devices have predominantly taken the shape of elongate or linearly extending pieces of equipment There have heretofore been provided three distinct types of static eliminators, each of which has its own deficiencies, as will be pointed out below. These three types are designated as inductive bars, electrically energized bars, and radio active bars.

Inductive static eliminator bars have the desirable feature that they require no outside source of power,

such as a source of electricity, or a radio active source. Such bars usually have a plurality of linearly extending conductive elements with pointed tips, known as points. These are directed to a moving web, and placed in proximity to it, and the points are all connected to ground by a suitable conductor, usually being mounted in a suitable carrier device of insulating material. They are relatively inexpensive, but have an operating requirement which limtis their usefulness. This operating requirment is that an inductive bar must reach a mimimal of threshold voltage, and serves no effective purpose below its threshold voltage. By way of example, if a particular inductive bar has a threshold voltage of 500 volts, it functions to eliminate static electricity from the moving web or sheet with which it is associated having a value above the threshold voltage 500 volts. Consequently, if the moving web or sheet has 1,500 volts of static electricity, the inductive bar will serve to reduce the static electricity voltage by 1,000 volts, down to the threshold voltage level. Therefore, there will remain on the moving web or sheet, in the present example, a static electricity charge of 500 volts. This is in many instances unsatisfactory.

While the inductive bar usually takes the form as de scribed above, other embodiments: of the inductive bar concept are known, including those in which a bar of metal is stamped out so as to provide a shape somewhat like a comb, with extending teeth or points, and it is also known to provide a plurality of tufts of fine wire bristles, spaced along the inductive bar, and all connected to ground.

Electrically energized static elimintors or static bars are widely used, being, however, more expensive than the inductive bars. These static bars are supplied with relatively high voltage alternating current, there typically being an electronic package associated with the bar, and containing a transformer or other voltage raising device. In these static eliminator bars, a plurality of points are provided in generally parallel array, and are either electrically connected to a conductor supplied with the alternating high voltage, or are capacitively connected to the conductor. A conductive shield or housing is provided in generally surrounding relationship to the central conductor, and in which the points extend, the housing having openings, with the sharpened terminals of the points being adjacent the openings.

The electrically energized static eliminator bars have a number of deficiencies, such as their leaving of nonneutralized stripes extending across the moving web from which the static is being eliminated, due to the relationship between the frequency of the alternating high voltage and the speed of the web: at high web speeds, the stripes of nonneutralized material exists. In order to overcome this deficiency, it has been proposed to use a dual system, including two static eliminator bars and two power units, which are electrically connected out of phase. Obviously, such a solution is even more expensive than the use of a single bar and its power unit or transformer'unit.

The electrically charged bars have the deficiency, also, of being over ridden, where the web of material is very highly charged. In this situation, the web is capacitive'ly coupled to the point and reverse charges the system, so as to actually over ride or turn off the bar. These bars require power units, which add to the expense, require high voltage wires, and also require related insulators, thereby adding to the expense and installation difficulty. The bars are often not readily placed at a desirable location in a particular machine, and cannot be easily relocated either to a different point within-the same machine, or to another machine. The electrically engergized static eliminator bars are not explosion proof, and in order to make them explosion proof, related equipment must be added, thereby adding to the expense. These bars are characterized by providing a constant amount of ionization, and are not capable, in the present state of the art, of being regulated with respect to the level of static present in the moving web. A further difficulty found with the presently used static eliminator bars which are electrically operated is that there must be space for insulating material in order to insulate the high voltage energy in the bar from ground; therefore, the end of the bar which is remote from the end in which the cable is led into the bar requires a relatively large insulator, with the result that the effective length of the. bar, as measured between the two outermost points of the bar, is less than the actual length or physical length of the bar. In practice, this has amounted to a reduction in the effective length, from the physical length of the bar, of approximately 2 to 3 inches, in such bars now in commercial use. This is a further deficiency, presenting a physical problem in certain machines where space is not available for a bar of a particular physical length with the result being that its effective length is less than the width of the material or web from which the static is being eliminated. This, therefore, leaves the two edges of the web material still statically charged.

Yet another deficiency-of the electrically energized high voltage static eliminator bars is that the high voltage equipment sends energy, known as spikes or high voltage radiation, which are false signals, to control circuits, thereby presenting undesirable problems.

Another embodiment of the static eliminator or static reducing bar which is known derives its energy from a supply of radio active material, which must be periodi- 3 cally recharged. The radio active static eliminator is expensive, and is subject to being deemed hazardous, even though it might have met all safety standards. The radio active bar has not achieved as wide an acceptance as has the electrically energized bar, receiving its energy from a high voltage source.

SUMMARY OF THE INVENTION The moving web energized static eliminator herein disclosed, in its preferred embodiment, includes a body of insulating material, in the form of a bar of generally rectangular cross section. Plexiglas has been found to be suitable insulating material. On one surface of the plexiglas insulating body is a plate of aluminum, having a grounding device, such as a screw, in engagement with it. On its opposite surface, there are a plurality of metal rings embedded in the Plexiglas bar so that each ring has an annular surface at the opposite surface of the plexiglas bar, and exposed to atmosphere. A point extends through the aluminum plate, in engagement with it, and thence through the plexiglas bar, being located concentrically within the conductive metal ring. The conductive point has a sharpenedor conical terminus portion, and its end is located near or below the plane of the surface of the plexiglas bar which includes the exposed surface of the conductive ring. The static eliminator so constructed is placed in adjacent, capacitive relationship to the moving web, so that the conductive ring or sleeve, which is electrically floating, is in ca- *pacitive relationship with the moving web. A second [-1 v ;capacitive' relationship exists between'the ring and the point, which is grounded by the aluminum plate and engaging screw.

j The present invention method includes the establishing ofa capacitive relationship between a moving material weband an electrically floating conductive member; and establishing a capacitive relationship between the floating conductive member and a grounded pointed conductive member. J

Among the objects of the present invention are to provide static eliminating or reducingapparatus of high "efficiency, and requiring no external electrical or radio active power source. I;

Another object of the present invention is the provision of such static equipment having a threshold level which is substantially negligible.

A still further object of the present invention is to provide static eliminating or reducing equipment of light weight, and low cost, and which is readily installed, and readily relocated.

A still further object of the present invention is the provision of static eliminating or reducing equipment in the form of a bar which will have an effective length of the present invention will be readily understood 7 from the following description, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view, with parts broken away, of a static reducing apparatus in accordance with the present invention.

FIG. 2 is a cross sectional view taken on the line 2-2 of FIG. 1.

FIG. 3 is a schematic illustration of the method of operation of the apparatus as shown in FIGS. 1 and 2.

FIG. 4 is an equivalent circuit diagram.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the drawings, wherein like or corresponding reference numerals are used for like or corresponding parts throughout the several views, there is shown in FIG. 1 apparatus 10 for reducing or eliminating the static electricity charge in a moving web of material. The apparatus 10 comprises a body 11 of insulating material, generally longitudinally extending and in the form of a bar, and having a rectangular cross-section. In the preferred embodiment, the body 11 is plexiglas. On one face of body 11 there is a plate 12 of conductive material, preferably aluminum.

Referring to FIG. 2, there may be seen the insulating body 11 and the conductive plate 12. Conductive plate 12 has a counter-bored aperture 13 extending therethrough, in which is located a screw 14, of conductive material, held in position by a nut 16, drawing the head of the screw against and into the counter-bored portion of the plate 12. As may be seen from the right hand portion of FIG. 2, an annular slot 17 has been formed in the surface 18 of the body 11, annular slot 17 extending only part way into the body 11 towards the plate 12. There has also been provided a bore 19 which extends through the body 11, being concentric with the annular slot 17, the bore 19 having an extension 19 intoand through the plate 12.

A point 20, of generally cylindrical configuration, and having a diameter slightly larger than the diameter of the bores 19 and 19, is driven into the bores 19 and 19, thereby serving to secure the plate 12 to the insulating body 11. The point 20 is sharpened at its end 21 which is at or slightly below the surface 18. A ring 25 is made of conductive material, such as aluminum, and is positioned in the slot 17 there being an annular surface 26 of the ring 25 which is substantially at the plane of the surface 18, so that both the surface 26 of ring 25 and the end 21 of point 20 are both exposed to atmosphere.

As will be readily understood, the rings 25 are electrically floating. That is, they are not connected to ground and they are not connected to any external source of power, such as a source of electricity. The points 20 are in engagement with the conductive plate 12, and are thereby grounded through the screw 14, when a conductor is connected to the screw and to ground, in conventional fashion.

In a preferred embodiment, the apparatus 10 may have a cross section of 1 inch by 1 inch, exclusive of the screw 14 and nut 16, and may be of any desired length. The points 20 may have a diameter of approximately 0.125 inches, and have their axes located approximately on centers spaced three quarters inch. The rings 25 may have an outside diameter of approximately fiveeighths inches and an axial length of approximately one-fourth inch. As thus constructed, the apparatus of FIGS. 1 and 2 is light weight and strong.

Referring now to FIG. 3, the apparatus is shown in schematic or diagrammatic form, and may be seen to include the point connected with ground, the conductive, electrically floating ring being in concentric surrounding relationship thereto, and with the end 21 thereof being in approximately the same plane as the surface 26 of rings 25. A web W of moving material is shown, and carries a charge of static electricity, indicated by the plus" signs thereon, although as will be appreciated the number and position of the plus signs is merely illustrative. The static electricity charge on the web W may be either a positive charge, as illustrated, or a negative charge. In FIG. 4, letter W and numerals 25 and 20 have been provided with prime marks, to indicate the relationship of the schematic circuit illustration of the method and apparatus, as related to FIG. 3. Thus, there is shown a capicitor 01 made up of a plate W and a second plate 25', being the representation, respectively, of the web W and conductive ring 25. The capacitor 02 is comprised of a plate 25' corresponding to the ring 25, and a second plate 20 corresponding to the point 20. The capacitor C-l has a value of approximately 100 pico pico farads, while the capacitor C-2 has a value of approximately 10 pico pico farads.

The apparatus It) depends upon the moving electro static field of the web W as a source of power, and as will be understood, the ring 25 and point 20 are placed within this field. As the static electricity charged web W passes the apparatus 10, the electrically floating conductive ring 25 picks up the static charge and converts it to voltage, in accordance with the basic formula:

where C is the capacitance in farrads q is the charge in coulombs and V is the voltage in volts. Expressing the relationship of the formula in a different manner,

from which it may be seen that the voltage on ring 25 is directly proportional to the amount of the charge on the web W. As a consequence, the voltage picked up by the floating conductive ring 25 will increase in value as the charge on the web W increases, so that thereby the apparatus 10 is self-regulating. Thus, the higher the value of the static field on the moving web W, the higher the voltage will be on the electrically floating conductive ring 25.

The voltage on the electrically floating conductive ring 25, increasing as the web W moves in relation to it, will seek a path to ground, and so the voltage in the ring 25 will flow to ground by passing through a conductive path comprised of the ions in the air between the ring 25, or its surface 26, and the end 21 of point 20, and thence into the point 20, and to ground. The air between the ring 25 and point 20 is broken down by the ionization, and there will thereby be produced ions which are attracted to the web W and combined with the charges on the web, to eliminate them. The energy being used to form the ions, derived from the moving web W, is constantly replenished by the movement of additional, charge web material into the region of the apparatus 10.

It is significant that the capacitor ring 25 will charge to the same polarity as the field in which it is placed, and as illustrated in FIG. 3, therefore, it will charge to a positive voltage. When this positive voltage flows to 6 the grounded point 20 it does so by a negative ionized path, thereby the result being that the ions generated are negative ions. It is negative ions which are attracted to the positively charged web W, and which combine with the positive or plus charges on the webs, so as to yield a substantially zero electric charge, due to the combining of the positive and negative ions.

The ring 25, having mass, will function as a voltage amplifier. Thus, if the electrostatic field of the moving web W is small, it will nevertheless charge the capacitor ring 25. As the web W continues to move, it will increase the voltage potential on the ring 25, continuing to convert charge to voltage, which will be stored by the ring 25. Consequently, there will be a build up of the value or potential of the capacitor ring 25 until ionization takes place in the manner above described. Further, as the energy is used up by the discharge from the electrically floating conductive ring 25 to the grounded point 20, it will be replenished by and from the moving field of the moving web W.

There has been provided an apparatus and method for reducing or eliminating the static electricity charge on a moving web of material, which does not require either a source of electricity or a radio active source for its energization, but derives its energy from the electrostatic field of a moving web of material. As will be appreciated, the herein disclosed apparatus and method automatically selects the ionization polarity in accordance with the polarity of the static electricity charge on the moving web, and also automatically selects the amount of ionization, a more heavily charged web causing the generation of more ions, while a lighter or lesser charged web results in the generation of a lesser amount of ions. The present apparatus and method cannot be outrun or over ridden by either a very highly charged web or a web moving at a very high speed, or both. As will be appreciated, with the present apparatus and method, in addition to there not being required an external power source, there is not required any external wiring, since the ground connection may be through the frame of a machine on which the apparatus is installed. The present invention method and apparatus provide for explosion proof operation, and the apparatus herein disclosed can be readily relocated either to another position within a machine, or to another machine. Further, the present invention apparatus does not require recharging, and the effective length of a configuration of the apparatus in bar form may be substantially as great as the physical length thereof. The present invention, also, avoids any interference with control circuitry at or near the installation of the apparatus herein disclosed.

In addition, as will be appreciated, the herein disclosed method and apparatus has no minimal or threshold voltage of significance, and will therefore serve to provide static elimination or static reduction in a moving web down to a level which is substantially insignificant.

It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification but only as indicated in the appended claims.

I claim:

1. Apparatus for reducing the static electricity charge in a moving web of material comprising:

means for causing said conductive plate means to be electrically floating, whereby said plate means is free of connection to ground and to electric poten tial source means, and

grounded electrically conductive means for causing with said plate means ionization of air adjacent said web including a point in capacitive relationship with said plate means.

2. The apparatus of claim 1, said conductive plate means comprisinga member in generally surrounding relationship to said point.

3. The apparatus of claim 2, and insulating means comprising a body of insulating material, said plate member being in said body with a surface thereof exposed to atmosphere.

4. The apparatus of claim 3, said point being in said insulating material body, said member being annular, and substantially concentric with said point.

5. The apparatus of claim 1, and insulating means comprising a body of insulating material, said conductive plate means and said grounded means being substantially embedded in said body and having a surface of said conductive means and the terminus of said grounded means exposed to atmosphere.

6. The apparatus of claim 5, a conductive plate on said body of insulating material remote from said terminus, said grounded means engaging said plate.

7. Apparatus for reducing the static electricity charge in a moving web of material comprising:

a. a body of insulating material,

b. floating electrically conductive plate means embedded in said body and having a surface thereof exposed to atmosphere,

0. electrically conductive point means in said body spaced from said plate means and having the terminus thereof in spaced capacitive relationship with exposed surface of said plate means for causing with said plate means ionization of air adjacent said moving web, and l d. means for connecting said point means to ground.

8. The apparatus of claim 7, said plate means being in generally surrounding relationship to said point means.

9. The apparatus of claim 8, said plate means being annular.

10. The apparatus of claim 9, said means for connecting said point means to ground comprising a conductive plate on said insulating body remote from said surface of said plate means.

11. The apparatus of claim 9, said point means extending at least partially through and engaging said conductive plate and said insulating body.

12. The apparatus of claim '7, said plate means comprising a plurality of annular elements. and a said conductive point means within and spaced from each said annular plate means.

13. A method for reducing the static electricity charge in a moving web of material comprising:

establishing a first capacitive relationship between said web and an electrically floating plate member,

establishing a second capacitive relatiohsip between the floating conductive plate member, and the point of a grounded conductive member across an air gap adjacent said web, and ionizing air by the discharge of voltage from said plate member to said point. 

1. Apparatus for reducing the static electricity charge in a moving web of material comprising: electrically conductive plate means for defining a capacitor with said moving web, means for causing said conductive plate means to be electrically floating, whereby said plate means is free of connection to ground and to electric potential source means, and grounded electrically conductive means for causing with said plate means ionization of air adjacent said web including a point in capacitive relationship with said plate means.
 2. The apparatus of claim 1, said conductive plate means comprising a member in generally surrounding relationship to said point.
 3. The apparatus of claim 2, and insulating means comprising a body of insulating material, said plate member being in said body with a surface thereof exposed to atmosphere.
 4. The apparatus of claim 3, said point being in said insulating material body, said member being annular, and substantially concentric with said point.
 5. The apparatus of claim 1, and insulating means comprising a body of insulating material, said conductive plate means and said grounded means being substantially embedded in said body and having a surface of said conductive means and the terminus of said grounded means exposed to atmosphere.
 6. The apparatus of claim 5, a conductive plate on said body of insulating material remote from said terminus, said grounded means engaging said plate.
 7. Apparatus for reducing the static electricity charge in a moving web of material comprising: a. a body of insulating material, b. floating electrically conductive plate means embedded in said body and having a surface thereof exposed to atmosphere, c. electrically conductive point means in said body spaced from said plate means and having the terminus thereof in spaced capacitive relationship with exposed surface of said plate means for causing with said plate means ionization of air adjacent said moving web, and d. means for connecting said point means to ground.
 8. The apparatus of claim 7, said plate means being in generally surrounding relationship to said point means.
 9. The apparatus of claim 8, said plate means being annular.
 10. The apparatus Of claim 9, said means for connecting said point means to ground comprising a conductive plate on said insulating body remote from said surface of said plate means.
 11. The apparatus of claim 9, said point means extending at least partially through and engaging said conductive plate and said insulating body.
 12. The apparatus of claim 7, said plate means comprising a plurality of annular elements, and a said conductive point means within and spaced from each said annular plate means.
 13. A method for reducing the static electricity charge in a moving web of material comprising: establishing a first capacitive relationship between said web and an electrically floating plate member, establishing a second capacitive relatiohsip between the floating conductive plate member, and the point of a grounded conductive member across an air gap adjacent said web, and ionizing air by the discharge of voltage from said plate member to said point. 